Ibuprofen, a non-steroidal anti-inflammatory drug (NSAID), has been used in humans for nearly forty years. While generally regarded as safe, ibuprofen and other NSAIDs can cause gastritis, dyspepsia, and gastric and duodenal ulceration. Gastric and duodenal ulceration is a consequence of impaired mucosal integrity resulting from ibuprofen-mediated inhibition of prostaglandin synthesis. This side-effect is a particular problem for individuals who take ibuprofen for extended periods of time, such as patients suffering from rheumatoid arthritis and osteoarthritis.
The risk of developing gastric or duodenal ulceration can be reduced by cotherapy with the drug famotidine. Famotidine blocks the action of the histamine type 2 (H2) receptor, leading to a reduction of acid secretion in the stomach. Reducing stomach acid with famotidine during treatment with certain nonsteroidal anti-inflammatory drugs is reported to decrease incidence of gastrointestinal ulcers (see Taha et al., 1996, “Famotidine for the prevention of gastric and duodenal ulcers caused by nonsteroidal anti-inflammatory drugs” N Engl J. Med 334:1435-9, and Rostom et al., 2002, “Prevention of NSAID-induced gastrointestinal ulcers” Cochrane Database Syst Rev 4:CD002296).
Although NSAID plus famotidine cotherapy reduces risk of developing gastric or duodenal ulceration, such therapies are not widely used. One explanation for this observation is that patient compliance is more problematic with a regimen that requires administration of two separate dosage forms. Efforts to develop a single unit dosage form comprising both ibuprofen and famotidine have been successful (see co-pending U.S. application Ser. Nos. 11/489,275, filed Jul. 18, 2006, 11/489,705, filed Jul. 18, 2006, and 11/779,204, filed Jul. 17, 2007), but were made more challenging by the discovery that ibuprofen and famotidine are chemically incompatible. Moreover, those dosage forms that have been described could be improved with respect to stability under “forced degradation” or “accelerated” conditions of elevated temperature and humidity. Forced degradation conditions are intended to accelerate the process of chemical degradation for a period of time and are used to predict the effect of storage under more benign conditions (e.g., room temperature) for a longer period of time.
There remains a need for new and improved unit dosage forms comprising ibuprofen and famotidine that exhibit exceptional stability under forced degradation conditions. The present invention meets that need.